Increasing speed from 50 mph to 60 mph = an average 12.4 percent drop in miles per gallon.

Increasing speed from 60 mph to 70 mph = an average 14 percent decrease in miles per gallon.

Increasing from 70 mph to 80 mph = another 15 percent drop in miles per gallon.

Faster than 80 mph = a 41 percent decrease in fuel efficiency compared to those cruising at 50 mph.

It's worth noting that the researchers found varying results depending on car models. That has much to do with the fact that theaverage fuel efficiency for cars has increased significantly as consumers' love for gas guzzlers has dwindled.

If you're looking to tone down the speed, some researchers have noted that drivers who listen to soothing tunes are better at keeping their cool behind the wheel.

You could always invest in a more fuel-efficient car while you're at it, too. Check out the DOE's list of its top ten EPA-rated rides.